SACSESS WP1.2 Performance Optimisation of Chemical Systems

Transcription

1 SACSESS WP1.2 Performance Optimisation of Chemical Systems M.A.Bromley, C.Boxall Engineering Lancaster University Lancaster LA1 4YW United Kingdom

2 Performance Optimisation of Chemical Systems Improve the understanding and optimise selected An / Ln extraction systems for safe and efficient operation Study of coupled mass transfer / interfacial kinetics Rotating Diffusion Cell (RDC) Derived from Lewis Cell Monitor both physical (diffusion, low to high sheer convection) and chemical (interfacial) kinetics Possibility to study separations based on kinetic selectivity (high sheer, low residence) rather than thermodynamic (low sheer, high residence) and the transition between the two regimes

3 Rotating Diffusion Cell - Apparatus Twin compartment for two separate solution phases Solution flux generated by rotation Defined interface area determined by membrane

4 Rotating Diffusion Cell - Modifications Commissioning & troubleshooting Eliminate pulley vibrations Redesign motor arm for stability Redesign PTFE baffle for improved solution flow and incorporated sampling port Augmentation Variable speed motor control Optical encoder & Arduino setup to provide live readout of motor shaft rotation speed (RPM & Hz)

5 Rotating Diffusion Cell - Membrane Mounting Millipore GSWP nitrocellulose membranes Range of pore sizes and thicknesses available Vary effective interface and flow rate Membrane mounted on RDC cylinder Methyl methacrylate-based adhesive Highly effective; membrane perimeter encased Appropriate mounting essential Avoid leakage through perimeter edge Resist application of damaging clearing solvent

6 Rotating Diffusion Cell - Membrane Pore Closure Porous structure of the nitrocellulose collapsed with clearing solvent 33.3% n-hexane 33.3% 1,2-dichloroethane 33.3% 1,4-dioxane Applied by pipette onto rotating membrane Defines porous interface area Treated area is transparent and non-porous Resulting membrane is under tension, aiding stability during rotation Variation of interface diameter allows for tuning of transfer rates through membrane

7 Rotating Diffusion Cell - Trans-membrane Ce Extractions Millipore GSWP047 nitrocellulose membrane mounted on RDC 0.2 µm pore size; 150 µm thickness; flow rate of 18 ml/min x cm 2 Rotation speeds of 0 10 Hz 3 porous interface diameters examined Ce(IV) extraction by TBP Aqueous phase 10 mm Ce(IV) (SO 4 ) 2 in 1 M nitric acid Organic phase 0.2 M TBP in kerosene Ce(III) extraction by TODGA Aqueous phase 10 mm Ce 2 (III) (SO 4 ) 3 in 1 M nitric acid Organic phase 0.2 M TODGA in 5% octanol : 95% kerosene

8 TODGA Synthesis In house manufacture Substantial cost reduction (Dr Dominic Laventine) Technocomm 2000 ( 2770) / 100 g 80% yield Lancaster 315 ( 436) / 100 g

9 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed Conditions 10 mm Ce(IV) 0.2M TBP in kerosene Interface diameter 20 mm 0-10 Hz rotation UV-Vis Abs monitoring 1 Hz / 60 rpm Abs 335 nm vs 0.2 M TODGA kerosene blank Peak Abs increases with time Ce(IV) extraction is occurring

10 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed 2.5 Hz / 150 rpm Abs 335 nm vs 0.2 M TODGA kerosene blank Peak Abs decreases as rotation speed increases

11 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed 5 Hz / 300 rpm Abs 335 nm vs 0.2 M TODGA kerosene blank Peak Abs decreases as rotation speed increases

12 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed 10 Hz / 600 rpm Abs 335 nm vs 0.2 M TODGA kerosene blank Peak Abs decreases as rotation speed increases Counter-intuitive increased flux expected to increase extraction rate

13 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed Very little extraction at 0 Hz no rotational flux Peak Abs, hence [Ce(IV)] aq, decreases as rotation speed increases No indication of saturation in extraction up to 120 min Indicative of high D-value for extraction OR extraction not reached completion

14 RDC Ce(IV)/TBP Extraction - Varied Rotation Speed Slope data from 0-60 min Interfacial flux Plot interfacial flux vs 1/SQRT(Hz) Approximate linearity Diffusion layer thickness, X D, increases with 1/SQRT(Hz) Extraction rate indicates Ce captured from diffusion layer Extractant diffusion into aqueous phase

15 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed Conditions 10 mm Ce(III) 0.2M TODGA in 5O:95K Interface diameter 20 mm 0-10 Hz rotation UV-Vis Abs monitoring 1 Hz / 60 rpm Abs 343 nm vs 0.2 M TODGA 5O:95K blank Peak Abs decreases as rotation speed increases

16 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed 2.5 Hz / 150 rpm Abs 343 nm vs 0.2 M TODGA 5O:95K blank Peak Abs decreases as rotation speed increases

17 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed 5 Hz / 300 rpm Abs 343 nm vs 0.2 M TODGA 5O:95K blank Peak Abs decreases as rotation speed increases

18 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed 7.5 Hz / 450 rpm Abs 343 nm vs 0.2 M TODGA 5O:95K blank Peak Abs decreases as rotation speed increases

19 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed 10 Hz / 600 rpm Abs 343 nm vs 0.2 M TODGA 5O:95K blank Peak Abs decreases as rotation speed increases

20 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed Same trend as Ce(IV)/TBP system, indicating that TODGA may have to partition into aqueous phase diffusion layer before extraction occurs Resulting [TODGA] gradient across diffusion layer Larger diffusion layer (slower rotation) allows greater penetration depth and hence more Ce(III) complexation

21 RDC Ce(III)/TODGA Extraction - Varied Rotation Speed Extraction appears to saturate after ~40 mins lower D-value than for Ce(IV)/TBP system total extraction of Ce achieved Saturation of diffusion layer?

22 Mixer-Settler Ce(III) / TODGA - Increasing [Ce(III)] Abs of organic phase vs 0.2M TODGA 5O:95K blank inverts at low [Ce(III)] Ce-TODGA complex increasing 343 nm Nitric-TODGA complex reducing 337 nm Necessitates HNO 3 contact pre-extraction

23 RDC Ce(III)/TODGA Extraction - Varied Interface Diameter Conditions 10 mm Ce(III) 0.2M TODGA in 5O:95K Interface diameters: 44 mm, 19.5 mm, 7.5 mm 10 Hz rotation UV-Vis Abs monitoring

24 RDC Ce(III)/TODGA Extraction - Varied Interface Diameter Extraction rate decreases with decreasing interface diameter, as expected Demonstrates a convenient control parameter Useful in assigning rate determining step when building model

25 Conclusions RDC system commissioned Ce(IV)/TBP system results indicate that rate of extraction is dependant on local hydrodynamics the greater the diffusion layer thickness, the faster the extraction rate Extracted entity captured from within diffusion layer initial diffusion of extractant into aq. phase from organic phase Key interaction between Ce(IV) & TBP occurs on the aq. side of phase boundary Similar results seen for Ce(III)/TODGA system with similar conclusions: Key Ce(III)-TODGA complexation occurs in aq. phase

26 Future Studies More detailed examination of Ce(III)/TODGA and Ce(IV)/TBP extraction systems using RDC Variation of [Ce] RDC experiments Variation of [HNO 3 ] in RDC experiments RDC Study of Eu(III)/TODGA extraction Build model determination of rate constants of interfacial transfer

27 QUESTIONS?

28 Mixer-Settler Ce(III) / TODGA - Increasing [Ce(III)] Abs of organic phase vs 5O:95K Strong ~340 nm Peak height increases with Ce(III) concentration and shifts slightly

29 Mixer-Settler HNO 3 / TODGA - Increasing [HNO 3 ] Abs of organic phase vs 0.2M TODGA 5O:95K blank Nitric-TODGA complex reducing 337 nm Necessitates HNO 3 contact pre-extraction